Railroad freight car structure

ABSTRACT

A railroad freight car has an underframe that includes a center sill and lateral cross-members such as bolsters, cross-bearers and cross-ties. Side sills run along the edges of the car. A floor sheet is welded to the center sill and side sills and above the cross-members. Floor stringers are welded to the top side of the floor sheet. A surface covering is mounted on top of the stringers. Thermal insulation may be installed between the surface covering and the floor sheets.

This application claims the benefit of the priority of U.S. Provisional Patent Application Ser. No. 63/002,879 filed Mar. 31, 2020, the specification and drawings thereof being incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to the field of railroad freight cars.

BACKGROUND

Railroad freight cars in the form of box cars have long been known in railroad use in North America. They generally have an underframe structure that is surmounted by a set of walls and a roof that define a housing in which to carry lading. The housing typically has doors on the side, although box cars with doors on both ends are also known. In box cars the underframe may include a center sill, a pair of spaced-apart side sills, and a set of lateral support members in the form of cross-bearers and cross-ties that extend between the center sill and the side sills. The cross-bearers and cross-ties often carry longitudinally-running stringers, and a nailable floor is often mounted on top of the stringers. The fabrication of this skeleton structure tends to require a large number of relatively short welds to secure the stringers to the cross-bearers and cross-ties. It may be difficult to maintain a relatively uniform level of welding in these welds, particularly if they are hand welded with not always optimal access for the welder.

SUMMARY OF THE INVENTION

In an aspect of the invention there is a railroad freight car. It has an array of spaced-apart cross-members. There is a floor sheet surmounting the cross-members. An array of stringers surmounts the floor sheet. There is a lading bearing surface mounted above the stringers.

In a feature of that aspect there is an array of cross-members includes at least a first cross-member having a flange and a web; the flange is spaced away from the floor sheet and the web extends between the flange and the floor sheet. In another feature, the web of the first cross-member has an uppermost margin welded to the floor sheet. In still another feature, the array of stringers includes at least a first stringer and a second stringer. The first stringer has a web that stands upwardly away from the floor sheet. The stringer has a flange surmounting the web of the stringer. In a further feature, thermal insulation is mounted above the floor sheet between the stringers and below the lading bearing surface. In still another feature, the floor sheet is imperforate. In another feature, the floor sheet defines an upper flange relative to the cross-members. In an additional feature, the cross-members have upstanding webs, and the upstanding webs have upper margins welded to the floor sheet.

In still another feature, the freight car has a straight-through center sill; the array of cross-members includes cross-members that extend laterally to either side of the center sill, and the floor sheet co-operates with the center sill to provide flange continuity across-the center sill. In an additional feature, one of (a) the straight through center sill has a top cover plate, and the floor sheet is mounted to co-operate with the top cover plate to provide flange continuity across the straight-through center sill; and (b) the floor sheet extends across the straight-through center sill.

In yet again another feature, the floor sheet forms an upper flange to the cross-members, and forms a lower flange of stringers of the array of stringers. In an additional feature, the cross-members have webs, and the webs of the cross-members have respective upper margins welded to the floor sheet. In an alternate feature, the stringers have respective webs standing upwardly from the floor sheet, and the webs have lowermost margins welded to the floor sheet. In a further feature, the stringers have respective webs standing upwardly from the floor sheet, and the webs have lowermost margins welded to the floor sheet. In another feature, the floor sheet has an array of apertures formed therethough. In yet another feature, the freight car is a box car having upstanding walls and a roof located upwardly of the floor sheet. In still another feature, the railroad freight car is an insulated box car.

In a further feature, the stringers, in cross-section, have a form that is one of: (a) an angle having a web standing away from the floor sheet and a flange mounted to the web, the flange being spaced away from the floor sheet; (b) a tube having at least one web standing away from the floor sheet and a flange mounted to the web, the flange being spaced away from the floor sheet; (c) a channel having a web standing away from the floor sheet and a flange mounted to the web, the flange being spaced away from the floor sheet; (d) an I-beam having a web standing away from the floor sheet and a flange mounted to the web, the flange being spaced away from the floor sheet; and (e) a T-bar having a web defining a stem standing away from the floor sheet and a flange mounted to the stem distantly from the floor sheet. In another feature of any of them, the web of the stringer is perforated. In still another feature, the lading bearing surface is a nailable floor. In another feature, the stringers, in cross-section, have a form that is a channel section under (c) that is a top-hat section having a back, two webs standing away from the back; and the webs having respective toes distant from the back. The toes having out-turned flanges.

In another aspect there is a railroad freight car. It has a matrix member that defines the upper flange of at least one of (a) a cross-tie; and (b) a cross-bearer of the freight car, while also forming a bottom flange of longitudinal stringers that support a floor covering thereof.

In still another aspect there is a method of constructing a railroad freight car wherein the method includes the steps of (a) welding a floor matrix sheet to underframe cross-members of the freight car; and (b) welding longitudinally extending stringers to the floor matrix sheet.

In a feature of that aspect, the cross-members have webs, and the method includes welding upper margins of the webs directly to the floor matrix sheet. In another feature, the longitudinally extending stringers have webs, and the method includes welding lowermost margins of the webs of the stringers to the floor matrix sheet. In still another feature, the method includes the step of installing insulation between the floor stringers above the floor matrix sheet. In a further feature, the method includes using automated welding apparatus to make continuous fillets along at least one of (a) the cross-members to attach them to the floor matrix sheet; and (b) the cross-ties to the floor matrix sheet. In a still further feature, the method includes inverting the floor matrix sheet between welding the cross-members and welding the stringers thereto.

These and other aspects and features of the invention may be understood with reference to the description which follows, and with the aid of the illustrations of a number of examples. The various features identified above may be combined with the aspects in many combinations and permutations.

BRIEF DESCRIPTION OF THE FIGURES

The description is accompanied by a set of illustrative Figures in which:

FIG. 1a is an isometric general arrangement view of a railroad box car from a first end, above, and to one side;

FIG. 1b is an isometric general arrangement view of the railroad car of FIG. 1a seen from one end, below and to one side;

FIG. 1c is a top view of the railroad box car of FIG. 1 a;

FIG. 1d is a bottom view of the railroad car of FIGS. 1a and 1 b;

FIG. 1e is a side view of the railroad box car of FIG. 1 a;

FIG. 1f is a sectional view on the longitudinal centerline of the car of FIG. 1 c;

FIG. 1g is an end view of the railroad box car of FIG. 1 a;

FIG. 1h is a view on transverse section ‘1 h-1 h’ of FIG. 1 c;

FIG. 1i is an enlarged detail of FIG. 1 g;

FIG. 2 is a perspective view of a scab section showing built-up layers of the floor structure of the railroad box car of FIG. 1 a;

FIG. 3a is an isometric view of a first example of floor stringer for the railroad box car of FIG. 1 a;

FIG. 3b is an alternative example of floor stringer to that of FIG. 3 a;

FIG. 3c is an alternative example of floor stringer to that of FIG. 3 a;

FIG. 3d is an alternative example of floor stringer to that of FIG. 3a ; and

FIG. 3e is an alternative example of floor stringer to that of FIG. 3 a.

FIG. 4 is an alternative example of floor assembly to that of FIG. 2.

DETAILED DESCRIPTION

The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples, of particular embodiments of the principles, aspects, or features of the present invention (or inventions, as may be). These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the specification, like parts are marked throughout the descriptive text and the drawings with the same respective reference numerals. The drawings are generally to scale, and may be taken as being to scale unless otherwise noted. Unless noted otherwise, the structural members of the car may be taken as being fabricated from steel.

The terminology used herein is thought to be consistent with the customary and ordinary meanings of those terms as understood by a person of ordinary skill in the railroad industry in North America. Following from decision of the CAFC in Phillips v. AWH Corp., the Applicant expressly excludes all interpretations that are inconsistent with this specification, and, in particular, expressly excludes any interpretation of the claims or the language used in this specification such as may be made in the USPTO, or in any other Patent Office, other than those interpretations for which express support can be demonstrated in this specification or in objective evidence of record in accordance with In re Lee, (for example, earlier publications by persons not employed by the USPTO or any other Patent Office), demonstrating how the terms are used and understood by persons of ordinary skill in the art.

In terms of general orientation and directional nomenclature, a Cartesian frame of reference may be suitable for describing a box car. For railroad cars described herein the longitudinal direction is defined as being coincident with the rolling direction of the railroad car, or railroad car unit, when located on tangent (that is, straight) track. The longitudinal direction may be taken as being the x-direction or x-axis. The transverse or lateral direction may be taken as the y-direction or y-axis. Unless otherwise noted, vertical, or upward and downward, being the z-direction or z-axis, are terms that use top of rail, TOR, as a datum. In the context of the car as a whole, the term lateral, or laterally outboard, or transverse, or transversely outboard refer to a distance or orientation relative to the longitudinal centerline of the railroad box car, or car unit, or of the centerline of a truck center. The term “longitudinally inboard”, or “longitudinally outboard” is a distance taken relative to a mid-span lateral section of the box car body.

The commonly used engineering terms “proud”, “flush” and “shy” may be used herein to denote items that, respectively, protrude beyond an adjacent element, are level with an adjacent element, or do not extend as far as an adjacent element, the terms corresponding conceptually to the conditions of “greater than”, “equal to” and “less than”. The directions correspond generally to a Cartesian frame of reference in which the x-direction is longitudinal or lengthwise, the y-direction is lateral or cross-wise, and the z-direction is vertical.

Given that the railroad box car described herein may tend to have both longitudinal and transverse axes of symmetry, a description of one half of the car may generally also be intended to describe the other half as well, allowing for differences between right hand and left hand parts. The abbreviation kpsi stands for thousand of pounds per square inch. To the extent that this specification or the accompanying illustrations may refer to standards of the Association of American Railroads (AAR), such as to AAR plate sizes, those references are to be understood as at the earliest date of priority to which this application is entitled. Unless noted otherwise, the underframe structure of the railroad car may be understood to be made of mild steel, and is generally of welded construction. Other materials, such as aluminum, are sometimes used, and components may be assembled by use of rivet or Huck (t.m.) bolts. The superstructure of the car is also typically made of mild steel sheet that has been formed and welded together, although aluminum and composite materials have also been used. Mild steel may be considered the default material.

By way of general definition, in general, a cross-bearer is a beam that carries a vertical load and that has a moment connection at which to carry bending moments in a load path into other primary structure, such as the center sill. Where a cross-bearer has a built-in moment connection, as illustrated, either to a center sill or to a side sill, there may be web and flange continuity into or across, or both into and across, that primary structural member. A cross-tie, by contrast, is typically not relied upon to transmit bending moment to other structure, but rather it analyzed as having simply supported ends, most often one end being at a side sill, and the other end being at the center sill. Cross-ties may be, an in the embodiment shown are, of shallower section in the vertical direction than the cross-bearers.

FIG. 1a shows a side elevation view of an example of a railroad freight car 20 that is intended to be representative of a range of railroad freight cars, such as may include box cars or flat cars or spine cars in which the presently described apparatus may be incorporated. Freight car 20 may be a single unit car. Freight car 20 may be an insulated box car, and may have a refrigeration unit.

In any event, freight car 20 may have a car body 22 that is carried on trucks 24 for rolling operation along railroad tracks. The trucks are spaced apart from each other longitudinally. Car body 22 may have first and second end sections 26. Each end section 26 has a main bolster 34 that seats on a respective truck 24 at a truck center CL. Freight car 20 has a center sill 30 that has draft sills longitudinally outboard of the Truck Centers, and has draft gear and couplers 32 mounted at either end for releasable connection to other railroad cars.

In freight car 20, center sill 30 may be, and in the embodiment shown in FIGS. 1a and 1b is, a straight-through center sill that extends from coupler to coupler. Main bolsters 34 extend transversely to center sill 30 at the respective truck centers. Spaced along freight car 20 is an array of cross-members 40. The array of cross-members extends laterally across the car between left hand and right hand side sills 50, at which the cross-members 40 terminate. That array of cross-members 40 may include, and in the embodiment illustrated does include cross-bearers 42 and cross-ties 44.

A floor sheet, or deck sheet, or deck 60, however it may be called, overlies the array of cross-members 40. Stringers 70 are mounted above floor sheet, or deck sheet, or deck 60. Stringers 70 run lengthwise in freight car 20, while cross-members 40 run cross-wise. Floor sheet or deck 60 functions as a bottom flange to stringers 70 and as a top flange to cross-members 40. That is, floor sheet or deck 60 carries longitudinal stresses (i.e., in the x-direction of freight car 20) in the context of its load carrying relationship with stringers 70, and transverse stresses (in the y-direction of freight car 20) in the context of its load carrying relationship with cross-members 40 (and relative to main bolsters 34, also). As shown, in this embodiment the floor sheet, i.e., deck 60, is located between the cross-members 40 of the underframe and overlying stringers 70. Expressed differently, the floor sheet is below the stringers.

In an insulated car, insulation 90 may be mounted between stringers 70, and a surface covering 80 of floor 28 is mounted above stringers 70, such that the insulation is between surface covering 80 and the floor sheet or deck sheet, or deck 60 however it may be termed. Surface covering 80 may be a consumable surface that is replaced from time to time. It may be a nailable surface, such as wood planking, or a nailable surface such as metal sheeting that can be puncture by nails, and that is intended for such nailable use.

To this point, the structure as described could be used in a flat car, or any car that has a deck upon which lading is secured. In the example shown, freight car 20 as shown is a box car having an upstanding wall structure 100 that forms a housing covering, and enclosing, deck 60. Wall structure 100 has first and second upstanding side walls 102, 104, and first and second upstanding end walls 106, 108, which co-operate to form a generally rectangular room. In the case of a box-car, walls 102, 104, 106 and 108 are full-height walls, and are covered by a roof assembly 110. Wall structure 100 includes top chords 112 that run along the tops of side walls 102, 104, and along long-side margins of roof assembly 110, i.e., the side walls 102, 104 and roof structure, or roof assembly, 110 are mated together at top chords 112. Wall structure 100 has access through first and second side door opening 114 mounted on either side of the car. Openings 114 are rectangular and have a door sill level flush with the inside floor height of car 20. Access to the inside of car 20 through openings 114 is governed by respective doors 116 mounted to either side of car 20, that are received in openings 114 when doors 116 are closed. As in the embodiment shown, doors 116 may be mounted on sliding tracks on either side of the car (i.e., they are sliding doors), and, when closed, doors 116 may form a sealed insulated plug when objects to be kept temperature controlled, are to be carried by freight car 20.

Side walls 102, 104 have sidewall sheets 118 that stand upwardly from side sills 50 and extend to mate with top chords 112. Side walls 102, 104 may have an array of longitudinally spaced stiffeners 122 that stand upwardly from side sills 50 and deck 60. Side walls 102, 104 may have inner and outer skins, and thermal insulation captured between those inner and outer skins. Roof structure 110 overspans deck 60 from side wall 102 on one side of the car, to the side wall 104 on the other side of the car, and from one end wall 106 to the other end wall 108.

In examining this structure more closely, center sill 30 has a pair of first and second upstanding webs 36, a bottom cover plate 38 and a top cover plate 58. They are welded together to form a rectangular box section as seen in FIGS. 1i and 2. First and second webs 36 are spaced apart symmetrically to either side of the longitudinal center line vertical plane of car 20. Bottom cover plate 38 is welded to webs 36, and forms the bottom flange of the center sill. Top cover plate 58 is welded to the upper margins of webs 36 and forms the upper flange of center sill 30. The margins of top cover plate 58 extend laterally beyond webs 36.

Cross-bearer 42 has a web 46 and a bottom flange 48. In the embodiment of FIGS. 1i and 2, the upper edge or margin of web 46 is welded to the underside of floor sheet or deck 60, such that deck 60 forms the upper flange of cross-bearer 42. In alternate embodiments, cross-bearer 42 could have a pair of spaced apart webs 46 such that a hollow rectangular section is formed. In a further alternative cross-bearer 42 could have an upper cover plate or flange welded to web (or webs) 36, and that flange could be welded to floor sheet 60. However, in the embodiment illustrated, the use of floor sheet 60 as the upper flange of the cross-bearer saves the weight, assembly, an expense of having a cross-bearer with upper and lower flanges. Thus a cross-bearer of inverted T-section of flange 48 and stem formed of 46, when mounted below, and in co-operation with the floor sheet 60 yields a structure that functions as if the cross-bearer has an upper flange carrying tensile and compressive loads in bending.

In this description, the floor sheet is located between the cross-members and the stringers. However, in context, the floor sheet functions as, and may be thought of as being part of the cross-members, namely the upper flange thereof. Likewise, as discussed below, it functions as, and may be thought of as being, the lower flange of stringers 70. Moreover, floor sheet 60 has another function, namely as forming the boundary of the lading supporting or lading containment enclosure structure of car 20 defined in the embodiment shown by the co-operation of deck or floor sheet 60 and the box car super-structure, namely wall structure 100. However notional it may be, and notwithstanding that floor sheet 60 can be termed as being part of the cross-members and at the same time as part of the stringers, in the context of this specification it is still “between” the stringers and the cross-members even while being part of them, inasmuch as it defines the boundary between them. In the context and terminology of this specification where either the cross-members or the stringers may lack a separate dedicated flange, it is correct to say, in context, both that floor sheet 60 forms part of the cross-members as their upper flange or part of their upper flange, and as part of the bottom flange of stringers 70 as their lower flange and as being located “between” the cross-members and the stringers in the context of forming a boundary layer between them.

Also, floor sheet 60 may be, or may form part of, the upper flange of main bolsters 34. That is, the main bolster has a web, or webs, 52, most often lying in a vertical plane or planes and extending upwardly of a bottom flange 54. There may be an upper flange 56 mounted underneath floor sheet 60, or floor sheet 60 may be mounted directed, as by welding, to the upper margins of web or webs 52. Both cross-bearers 42 and main bolsters 34 have moment connections to center sill 30.

In respect of the connection to center sill 30, cross-bearers 42 have flange continuity as between bottom flange 48 and bottom cover plate 38 of center sill 30. There is also web continuity through center sill 30 provided by internal web gussets 66. There is flange continuity provided by the mating of floor sheet 60 with top cover plate 58. In an alternate embodiment, floor sheet 60 may form the top cover plate of center sill 30, as where the upper margins of webs 36 are welded to floor sheet 60, and floor sheet 60 is continuous across car 20.

As with cross-bearers 42, cross-ties 44 each have a web 62 (or, alternatively, two webs 62) and a bottom flange 64. There may also be web continuity through center sill 30, and a flange continuity connection between floor sheet 60 and center sill top cover plate 58. There is web continuity of cross-ties 44 through center sill 30 as indicated by internal gussets 66 that are coplanar with, or substantially coplanar with, respective webs 62 of cross-ties 44.

Main bolster 34, cross-bearers 42 and cross-ties 44 have laterally outboard ends that mate with side sills 50. Each of side sills 50 has an L-shaped angle iron form, with a first leg 72 and a second leg 74. First leg 72 is a vertical leg that form the vertical web of side sill 50. Second leg 74 is a leg that extends laterally inwardly from the lower end of the vertical leg. Gussets 76 are mounted within the curve of side sill 50 in the plane of each web 46 of cross-bearers 42 and provide web continuity between bottom flange 48 and legs 72 and 74 of side sill 50.

The upper edge of the webs of cross-bearers 42 and cross-ties 44 are notched to receive a lengthwise running member 68. Lengthwise running member 68 may be, and as show is, a flat bar that abuts, and is welded to, the vertical wall formed by first leg 72. As welded in place flat bar 68 acts as a flange in opposition to second leg 74, and also forms a sill that forms the footing for side wall stiffeners 122, and forms a land overlapped by the outboard edge of floor sheet 60, and to which that edge is welded, defining its outboard boundary condition.

With floor sheet 60 in place, the array of stringers 70 mounted above floor sheet 60. Stringers 70 have a first leg 82 and a second leg 84. First leg 82 has a lower end welded to floor sheet 60. First leg 82 stands upwardly from floor sheet 60. Second leg 84 is attached to, and forms a laterally extending flange relative to first leg 82 and is spaced apart from and parallel to deck or floor sheet 60. Stringers 70 run lengthwise from end to end of car 20. The spacing between the flange defined by second leg 84 and floor sheet 60 may correspond to, and in the example illustrated does correspond to, the thickness of thermal insulation installed between successive pairs of stringers.

Surface covering 80 is mounted atop the flanges of stringers 70. As noted, surface covering 80 may be of the form of wooden planking, planking formed of nailable polymer or composite materials, or of nailable steel panels or aluminum extrusions or sheeting.

Stringers 70 may have different forms. FIG. 3a shows the angle iron form of stringer 70 seen in FIGS. 1i and 2. It could, alternatively, have the form of an angle iron as seen in FIG. 3e in which the vertical web of first leg 82 is perforated with apertures or openings 86 such as may reduce the overall thermal conductivity of stringer 70, and so therefore the heat loss through the stringer. Although diamond shaped openings are shown, other shapes could be used to reduce the material in the web and thereby constrict the thermal conduction heat transfer path through stringers 70. Alternatively, stringers 70 could have the form shown in FIG. 3b in which a rectangular tube is employed, which may be a seamless steel tube of a thin-walled formed steel section 88 having vertical legs 92 and horizontal flanges 94. In an alternative embodiment, the bottom side of the rectangular section may be omitted, and the remaining three-sided channel can be welded toes-down to floor sheet 60. In either alternative, as before, stringer 70 is welded to run lengthwise along floor sheet 60. Section 88 may also be perforated with apertures or openings 86 as shown in FIG. 3e . In the further alternative of FIG. 3d , stringer 70 may have the form of a channel section 96 with one leg welded to floor sheet 60. The upstanding web may have apertures or openings 86 formed therethrough. Yet further, as in FIG. 3c , stringer 70 may have the form of an I-beam or wide-flanged beam 98 in which one flange is welded to floor sheet 60, and surface covering 80 is carried on the other flange. Again, the web may be perforated to reduce heat transfer.

New box car builds can have nailable steel floors. In the past, such floors have been made of hardwood. In such an underframe example, longitudinal stringers are supported directly by the cross-bearers and cross-ties. In this structure, the stringers are connected to the cross-bearers, cross-ties, and floor by a large number of short welds, typically less than about 2 inches in length. By contrast, in the example, or examples, described in this specification, the use of a structural floor plate, i.e., floor sheet, deck sheet, or “deck” 60, which eliminates the traditional I-beam stringers that were welded to the upper flanges of the crossties and cross-bearers. Floor stringers 70 are used instead. Floor stringers 70 are added to the structure above floor sheet 60 to provide support to the floor material of surface covering 80. In the various Figures surface covering 80 is shown as wood, but other floor systems such as aluminum extrusions could be used, where suitable in the context of the lading to be carried. The structural floor sheet 60 may allow the crosstie and cross-bearer webs to be mounted directly to the floor sheet, eliminating the top flange from these structural components. This may tend to reduce the amount of steel used in the design, and may eliminate a number of welds. Furthermore, of the welds that remain to be made, the design may permits welding to be continuous rather than the small, short, hand welds previously made, i.e., to allow for uninterrupted long weld fillets made by automated equipment. It may also tend to simplify the structure, and to simplify the assembly of that structure. This approach may be well suited to insulated cars, with a higher floor sheet than may otherwise be customary. A lighter structure may also permit a longer, more volumetrically capacious car to be built, capable of carrying more lading. Where, for example, the use of pallets is contemplated, increasing car length from 68′-6″ to 72′-0″ may be helpful.

In each of the examples of FIGS. 3a to 3e , stringers 70 are welded along the floor sheet 60. In the method of manufacture of this railroad car, when floor sheet 60 is mounted to the cross-members, the underframe of car 20, namely the structure that includes center sill 30, side sills 50, bolsters 34, and cross-members 40, is turned upside-down and continuous welds can be made by machine along the respective fillets. The assembly is then rotated so that the floor sheet faces upward. Fillets are welded along the margins of the sheet to connect to center sill top cover plate 58 and to longitudinally running member 68. Stringers 70 are placed in jigs and positioned on floor sheet 60, and then continuous longitudinal welds are made by automated welding machines to produce relatively consistent quality welds. This may tend to improve the rate at which welding occurs, and it may tend to improve the quality and consistency of the welds. In each case, the method includes welding the cross-members to one side of floor sheet 60, and then welding the stringers to the opposite side of sheet 60. This permits the welding to include the step of making long continuous fillet welds along the stringers (and along the cross-members) and of making those long fillets with automated welding equipment.

To that end, floor sheet 60 may in some instances not be a continuous sheet, but rather may be thought of as a continuous matrix member 120, with cross-members 40 welded to one side and stringers 70 welded to the other side. Matrix 120 is shown in an alternate form in FIG. 4 as a perforated lattice work 124. Perforated lattice work 124 has a waffle-shaped pattern of intersecting lateral and longitudinal strips 126, 128 with interstitial openings 130 between the various pairs of strips in the lengthwise and cross-wise directions. Stringers 70 are welded amidst the top sides of respective longitudinal strips 128, and cross-members 40 are welded to the underside of respective lateral strips 126 during the steps of welding of the cross-members and stringers, respectively, may occur. In this instance, the openings may be covered with polymeric sheeting inserted to lie above lattice work 124, and the internal space filled with foam installation afterward.

In the example of FIGS. 1a and 1b , freight car 20 is shown as being a regular box car with a single level, constant height deck or floor sheet 60 from end to end. In this car, the primary structure of a straight-through center sill forming the spine of the underframe is accompanied by cross-bearers and cross-ties that extend from the center sill to the side sills. However, in an alternate embodiment car 20 could be a drop-center car having stub sills at either end, and a depressed center section with a lower floor. In such a car, in the central portion the cross-bearers and cross ties may run the full width of the car without interruption by, or connection to, a center sill, or there may be a center sill that is shallower in through-thickness under the center portion of the car. Such as center sill of shallow depth may be of greater width than the draft sills at either end of the car longitudinally outboard of the Truck Centers.

Various embodiments have been described in detail. Since changes in and or additions to the above-described examples may be made without departing from the nature, spirit or scope of the invention, the invention is not to be limited to those details. 

We claim:
 1. A railroad freight car comprising: an array of spaced-apart cross-members; a floor sheet surmounting the cross-members; an array of stringers surmounting said floor sheet; and a lading bearing surface mounted above said stringers.
 2. The railroad freight car of claim 1 wherein said array of cross-members includes at least a first cross-member having a flange and a web; said flange is spaced away from said floor sheet; and said web extends between said flange and said floor sheet.
 3. The railroad freight car of claim 2 wherein said web of said first cross-member has an uppermost margin welded to said floor sheet.
 4. The railroad freight car of claim 1 wherein said array of stringers includes at least a first stringer and a second stringer; said first stringer has a web that stands upwardly away from said floor sheet; and said stringer has a flange surmounting said web of said stringer.
 5. The railroad freight car of claim 1 wherein thermal insulation is mounted above said floor sheet between said stringers and below said lading bearing surface.
 6. The railroad freight car of claim 1 wherein said floor sheet is imperforate.
 7. The railroad freight car of claim 1 wherein said floor sheet defines an upper flange relative to said cross-members.
 8. The railroad freight car of claim 7 wherein said cross-members have upstanding webs, and said upstanding webs have upper margins welded to said floor sheet.
 9. The railroad freight car of claim 1 wherein said floor sheet has an array of apertures formed therethough.
 10. The railroad freight car of claim 1 wherein said freight car has a straight-through center sill; said array of cross-members includes cross-members that extend laterally to either side of said center sill; and said floor sheet co-operates with said center sill to provide flange continuity across-said center sill.
 11. The railroad freight car of claim 10 wherein one of: (a) said straight through center sill has a top cover plate, and said floor sheet is mounted to co-operate with said top cover plate to provide flange continuity across said straight-through center sill; and (b) said floor sheet extends across said straight-through center sill.
 12. The railroad freight car of claim 1 wherein said floor sheet forms an upper flange to said cross-members, and forms a lower flange of stringers of said array of stringers.
 13. The railroad freight car of claim 12 wherein said cross-members have webs, and said webs of said cross-members have respective upper margins welded to said floor sheet.
 14. The railroad freight car of claim 12 wherein said stringers have respective webs standing upwardly from said floor sheet, and said webs have lowermost margins welded to said floor sheet.
 15. The railroad freight car of claim 13 wherein said stringers have respective webs standing upwardly from said floor sheet, and said webs have lowermost margins welded to said floor sheet.
 16. The railroad freight car of claim 1 wherein said freight car is a box car having upstanding walls and a roof located upwardly of said floor sheet.
 17. The railroad freight car of claim 1 wherein said railroad freight car is an insulated box car.
 18. The railroad freight car of claim 1 wherein said stringers, in cross-section, have a form that is one of: (a) an angle having a web standing away from said floor sheet and a flange mounted to said web, said flange being spaced away from said floor sheet; (b) a tube having at least one web standing away from said floor sheet and a flange mounted to said web, said flange being spaced away from said floor sheet; (c) a channel having a web standing away from said floor sheet and a flange mounted to said web, said flange being spaced away from said floor sheet; (d) an I-beam having a web standing away from said floor sheet and a flange mounted to said web, said flange being spaced away from said floor sheet; and (e) a T-bar having a web defining a stem standing away from said floor sheet and a flange mounted to said stem distantly from said floor sheet.
 19. The railroad freight car of claim 18 wherein said stringers, in cross-section, have a form that is a channel having a web standing away standing away from said floor sheet and a flange mounted to said web, said flange being spaced away from said floor sheet, and said channel is a top-hat section in which said channel has a back, two webs standing away from said back; and said webs having respective toes distant from said back, said toes having out-turned flanges.
 20. The railroad freight car of claim 12 wherein said stringer has a web and said web of said stringer is perforated.
 21. The railroad freight car of claim 1 wherein said lading bearing surface is one of (a) a nailable floor; (b) an aluminum extrusion; (c) aluminum decking; and (d) wood decking.
 22. A railroad freight car that has a matrix member that defines the upper flange of at least one of (a) a cross-tie; and (b) a cross-bearer of said freight car, while also forming a bottom flange of longitudinal stringers that support a floor covering of said railroad freight car.
 23. A method of constructing a railroad freight car wherein said method includes the steps of (a) welding a floor matrix sheet to underframe cross-members of said freight car; and (b) welding longitudinally extending stringers to said floor matrix sheet.
 24. The method of claim 23 wherein said cross-members have webs, and said method includes welding upper margins of said webs directly to said floor matrix sheet.
 25. The method of claim 23 wherein said longitudinally extending stringers have webs, and said method includes welding lowermost margins of said webs of said stringers to said floor matrix sheet.
 26. The method of claim 23 wherein said method includes the step of installing insulation between said stringers above said floor matrix sheet.
 27. The method of claim 23 wherein said method includes using automated welding apparatus to make continuous fillets along at least one of (a) said cross-members to attach them to said floor matrix sheet; and (b) cross-ties to attach them to said floor matrix sheet; and (c) a bolster to attach it to said floor matrix sheet.
 28. The method of claim 23 wherein said method includes inverting said floor matrix sheet between welding said cross-members thereto and welding said stringers thereto. 